1. Field of the Invention
The present invention relates to a preliminary ventilating device for vehicles which is of the type which employs, for example, solar cells and a storage battery which is secondary cells as auxiliary and main power sources, respectively.
2. Prior Art
Japanese Patent Publication No. 51451/1984 discloses a vehicle in which parking ventilation is performed, i.e., the interior thereof is ventilated while the vehicle is parked, by a ventilation fan serving as ventilation means which is driven by the electromotive force from a solar battery.
Japanese Patent Laid-Open No. 1-172016 discloses a ventilation system for vehicles to eliminate an excessive increase in the temperature of the interior of the vehicle which occurs when the vehicle has been parked for a long time under a scorching sun in summer time, because it makes a driver or passenger uncomfortable when they get in the vehicle and it takes some time for an air conditioner to lower the temperature to a comfortable level. In Japanese Patent Laid-Open No. 172016, a ventilation fan, serving as ventilation means, automatically operated when the temperature of the interior of the parked vehicle reaches a predetermined value or above, is provided, and parking ventilation is performed, i.e., the air in the interior of the vehicle is replaced with fresh air, by the operation of such a ventilation fan. This ventilation fan is driven by the solar battery which sends out an output voltage corresponding to the amount of sunlight it receives.
Ventilating fans are driven by a d.c. motor. FIG. 15 shows an activation characteristic curve of this d.c. motor for the ventilating fans and voltage-current characteristic curves of the solar battery. As can be seen in FIG. 15, although a d.c. motor activation characteristic curve R generally exhibits a proportional tendency, it has a first current peak RA and a second current peak RB at low voltages. Hence, to activate the d.c. motor, current and voltage are continuously and gradually increased toward the first peak RA from a low voltage, and the motor is activated when the first peak RA has been reached. The present inventors call this generally employed activation method "gradual starting".
The solar battery output voltage and current characteristic Y varies depending on the amount of sunlight the solar battery receives. When the amount of sunlight that the solar battery receives is a maximum, like, for example, in summertime, the solar battery generates a voltage current characteristic Y1 indicated by the broken line. As the amount of sunlight that the solar battery receives decreases, voltage and current on the voltage and current characteristic generated by the solar battery decrease substantially uniformly, that is, the solar battery generates a voltage current characteristic Y2 or Y3. To activate the d.c. motor reliably using a solar battery exhibiting the voltage current characteristic Y, an activation method different from the aforementioned one is employed. In this method, an open voltage current of the solar battery which serves as a reference for determination of the voltage current characteristic is measured, and then voltage and current required for activation are applied to the d.c. motor simultaneously. Hence, the present inventors call this activation "simultaneous start".
The present inventors have confirmed that this simultaneous starting method is particularly effective when a voltage current characteristic Y contains the first and second peaks RA and RB within its range. It has also been confirmed that the motor can be activated not only by a solar battery which exhibits the voltage current characteristic Y1 containing both the first and second peaks RA and RB in its range but also by a solar battery which exhibits the voltage current characteristic Y2 containing only the lower second peak RB in its range.
When a sufficient amount of sunlight cannot be obtained and only the voltage current characteristic Y3 of the solar battery is obtained, since the voltage current characteristic Y3 does not exceed the second peak RB, the aforementioned simultaneous starting cannot be performed.
If simultaneous activation is attempted when the voltage current characteristic Y3 is obtained, simultaneous activation cannot succeed and the d.c. motor is rendered in a locked state in which a rotor and a stator are magnetically attracted to each other. Such a locked state may not be released even if the amount of sunlight gradually increases afterwards and the solar battery recovers an electromotive force exhibiting the voltage current characteristic Y2 which allows for simultaneous starting.
There has been a demand for quick reduction in high temperatures of the compartment of the vehicle by ventilation even when a sufficient amount of sunlight cannot be obtained, like in the morning in summer or in a tropical region.
To meet such a demand, activation of the ventilating fans must be initiated when the amount of sunlight is not sufficient but when the electromotive force of the solar battery has increased to a certain value.